In prior art motor control systems, an AC mains voltage input is first rectified to provide a DC voltage output. The DC output voltage is used by an inverter to generate a three-phase AC output which drives the system motor. The frequency of the three-phase inverter output, and hence the motor speed, can be adjusted by regulating the DC voltage output from the bridge rectifier. In some of these prior art systems, the first 30.degree. to 60.degree. of each phase of the AC mains voltage input is devoted to computing the desired conduction angles for the bridge rectifier SCR's. Such a configuration of necessity sacrifices a portion of each AC mains voltage phase, which portion could otherwise be used to supply operating power for the system.